An IPOD® ear plug in one ear and a cell phone at the other ear is a most fashionable way to drive. Such a driver, however, can potentially block an emergency vehicle trying to thread its way through traffic.
Other reasons why drivers do not get out of the way are that the radio is turned up, the windows are up, or the internal rear view mirror is turned to reflect back to the driver such that the pulsing light of the ambulance is not seen, or the driver is relatively hard of hearing.